This application is related to concurrently filed U.S. application Ser. No. (23336), entitled xe2x80x9cSpindle Mounting for Aluminum Wheel Carrierxe2x80x9d.
The present invention relates in general to spindles for wheel mounting in automotive vehicles, and, more specifically, to the attachment of cast iron or steel spindles to cast aluminum wheel carriers.
The use of lightweight materials in automotive vehicles is desired wherever possible in order to help increase fuel economy. Thus, the use of aluminum instead of iron or steel in vehicle suspension components is of increasing interest to vehicle manufacturers. However, the material properties of aluminum can be very different from those of iron or steel, meaning that aluminum cannot be directly substituted in every component in a straightforward way.
A vehicle suspension includes a spindle to which a wheel hub is mounted. The spindle is mounted to a wheel carrier such as a knuckle, axle, or other component. Due to strength and heat transfer requirements, the spindle is typically made of steel or iron. Prior art spindles have previously been made as an integral forging/casting with their carrier or have been mounted to their carriers by threading or welding, for example.
Another method for mounting a spindle has been to press-fit the spindle into a bore on the wheel carrier. The interference between the spindle and the bore (i.e., the bore diameter is slightly less than the spindle diameter) creates an elastic deformation force against the spindle to retain it.
One hurdle in the possible use of aluminum castings for wheel carriers has been the lack of an easy method to attach the spindle. Prior art mounting methods have been unsuccessful due to the distinct properties of steel/iron versus aluminum, such as different thermal properties and aluminum""s different elastic deformation.
The present invention adapts a press-fit method of attachment for an iron or steel spindle to an aluminum wheel carrier, resulting in overall weight savings for a vehicle. As used herein, xe2x80x9caluminumxe2x80x9d includes any alloy principally comprised of aluminum.
In one aspect of the invention, a wheel assembly for a vehicle comprises a spindle and a wheel carrier. The spindle includes a shank portion and a shoulder portion. The shank portion includes a press-fit portion adjacent the shoulder portion and has a first predetermined diameter. The wheel carrier is adapted to be supported by a suspension system of the vehicle. It is comprised of aluminum and has a spindle-receiving bore therethrough. The bore has an initially-formed diameter smaller than the first predetermined diameter. The press-fit portion is press-fit into the bore. The difference between the initially-formed diameter and the first predetermined diameter is sufficiently large that the press-fit portion is surrounded by a deformation zone having a radial thickness of at least 10 microns. In one preferred embodiment, this deformation zone is comprised of both plastically and elastically deformed aluminum.